A silicone-based resin composition or a polyisobutylene-based resin composition, which has a silanol group or a reactive silyl group at a terminal and forms a siloxane bond by hydrolysis and a condensation reaction, is widely used in a variety of fields since a cured material thereof is excellent in properties such as weatherability, durability, heat resistance and cold resistance, and particularly, a modified silicone-based resin composition is used in high volume as sealing agents, adhesives, floor materials, waterproof materials and coating materials in the field of architecture. Particularly, in recent years, a siding board is used in place of use of a wall clay, and therefore demands for modified silicone-based sealing material increase rapidly. When the siding board is used, since the board is large, there is a problem that a gap is generated between the board and the sealing material to cause joint cuts due to contraction of the board. The siding board is often attached to a vertical portion, and naturally, it is necessary that the sealing material does not hang down between application of the sealing material and curing of the sealing material and has a high thixotropic property to avoid the influence on workability during application.
In order to impart thixotropic characteristics, colloidal silica has been used, however, it includes many problems that it produces cracks or it has a very high modulus after curing to cause deterioration of the following character to an adherend. Further, in order to retain adhesion between the sealing material and the siding board, a sealing material having a low modulus, in which a restoring force is weakened by adjusting a catalyst, is used. In this case, there is a problem that the following character to elongation and contraction of the siding board is increased after the execution of work, restoring force, a restoring force and strength of the sealing material are reduced.
Further, in order to impart a thixotropic property or a following character for a joint, a chain-like surface-treated calcium carbonate is also proposed (Patent Document 1). Moreover, it is reported that as this type of surface-treated calcium carbonate filler, a surface-treated calcium carbonate, which is formed by surface-treating calcium carbonate with metal soap of a saturated fatty acid, metal soap of an unsaturated fatty acid or metal soap of an aliphatic carboxylic acid by a wet process, and reducing extremely the alkali metal content, imparts an excellent thixotropic property, slump resistance and good storage stability to the curable resin composition (refer to Patent Documents 2 and 3). Moreover, it is reported that a surface-treated calcium carbonate, which is surface-treated with a surface-treating agent made from non-metallic soap, has an excellent thixotropic property and slump resistance in the curable resin composition, and imparts excellent storage stability and adhesion properties not seen before (refer to Patent Document 4).
Further, a surface-treated calcium carbonate filler, in which the amount of the fatty acid salt having a counter ion of monovalent is markedly increased, is also provided (refer to Patent Document 5).